Frequency Histogram

A frequency histogram is a graph that uses vertical columns to show the number of times an event occurs, known as frequency. It is thus used to graphically show the result of a frequency distribution in grouped data. Similar to all histograms, there is no space between the bars in a frequency histogram.

It helps us to identify the most preferred event(s) in all.

How to Make a Frequency Histogram

Let us draw and interpret a left-skewed histogram involving the number of days a group of 20 students present in a class.

28, 27, 29, 27, 29, 30, 29, 29, 27, 29, 27, 28, 29, 30, 28, 29, 28, 30, 28, 29

Arranging the continuous data in ascending order, we get

26, 27, 27, 27, 28, 28, 28, 28, 28, 29, 29, 29, 29, 29, 29, 29, 29, 30, 30, 30  

If we draw a frequency table with the above data, we get the following:

Preparing the frequency histogram with the above data, we get the following:

The histogram shows that 30 is the most preferred event in the given distribution. We also conclude that 8 out of 20 students attend 30 days, which is the most among all the events.

Let us solve another example using the frequency histogram:

Solved Example

Sketch a frequency histogram with the data showing the number of movies 20 students had seen in a month. Then, find how many movies are seen by most students. (Hint: Make the frequency table).

2, 3, 1, 1, 3, 2, 5, 4, 1, 2, 2, 2, 3, 3, 1, 4, 2, 4, 3, 2

Arranging the continuous data in ascending order and then making the frequency table, we get
1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5

Sketching the frequency histogram using the frequency table, we get
From the histogram,  7 students had seen 2 movies each, which is the most by any number of students.